Current limiting circuits are employed as protection in many applications, such as power regulators, voltage sources, and current sources. Most current limit/protection circuits sense a load current associated with a power transistor for the particular application. Typically, a sense resistor is series-coupled to the load for sensing the load current. However, configuring a sense resistor in series with the load may result in power loss, heat dissipation, and other undesirable conditions.
Other current limiting circuits mirror current flowing through a power MOSFET with a mirror MOSFET. Also, circuitry is employed to substantially reduce the effect of channel modulation on the mirrored current by keeping the power and mirror MOSFETs' drain-source voltages relatively equal. However, extensive current mirroring can introduce undesirable poles into an open loop frequency response of a current limiting circuit. Also, the accuracy of this circuit can be diminished by component mismatch.